The Imperial War Museum tells the story of Britain at war, from World War One to the present, through a collection of 10 million items – from guns to planes to medals to cyanide pills – at five locations in England visited by over 2 million people every year.

In this episode, we descend into Churchill’s top secret underground bunker to discover why he was an irreplaceable leader. We find out how a London housewife became a spy who withstood horrific Nazi torture to protect a vital secret, then take cover in a World War One trench as we reveal the story of a Nobel Prize winning physicist whose discovery turned the tide of the war. We meet an aging cold warrior who exposes dark truths about atomic weapons hidden from the British people for 50 years, then fly above Iraq with British top guns to discover how to stay frosty when enemy missiles lock on. And finally we follow a team of military researchers as they close in on the holy grail of camouflage: how to make a soldier invisible.